1. Field of the Invention
The present invention relates to the timing adjusting technologies, and it particularly relates to timing-adjusting method and apparatus and diversity receiving method and apparatus with which to adjust the timing of a plurality of signals received by a plurality of antennas so as to carry out the diversity reception.
2. Description of the Related Art
In digital radio communication, signals transmitted from a transmitting apparatus travel through radio propagation paths before they are received by a receiving apparatus. The receiving apparatus extracts information symbols, which are the object of transmission, from the signals received. In order to extract such information symbols accurately, the receiving apparatus must carry out extraction with a timing synchronized with the timing of the information symbols sent from the transmitting apparatus (hereinafter referred to as “synchronous timing”). Generally, a receiving apparatus, which is not informed of a synchronous timing from a transmitting apparatus, extracts one from the signals it has received. However, where the signals transmitted between a transmitting apparatus and a receiving apparatus are multi-carrier signals, application of an extraction method of synchronous timing for single-carrier signals may result in an increase in the amount of processing with the increase in the number of carriers. On the other hand, one of the methods for suppressing the amount of processing, which results from the extraction of synchronous timing for multi-carrier signals, is such that the correlation value between the pilot signal contained in the received signals and the pilot signal prepared beforehand is calculated and the timing when the peak of the correlation value is attained is extracted as the synchronous timing (See, for example, Reference (1) in the Related Art List below).
Related Art List
(1) Japanese Patent Application Laid-Open No. Hei8-46659.
To improve the quality of signal transmission, a receiving apparatus may be provided with a plurality of antennas and a plurality of signals received by the plurality of antennas may be subjected to a diversity processing, or sometimes a combining diversity processing. In such a case, timing errors of the respective antennas may add up and, therefore, they are likely to lead to larger timing errors. If the difference in timing between antennas becomes large, the received signals rotates, and a combining diversity processing for the rotated signals may not result in any improvement in the transmission characteristics of signals. With multi-carrier signals, the rotation occurs with the sub-carriers, so that a combined diversity processing between sub-carriers with opposite phases may lead to a worsening of transmission characteristics of signals.